Mr Craig, a property developer, was worth a net $5 million.
He had reviewed the budget and knew there was enough money until polling day.
This election, others were contributing to the party coffers and party volunteers were spending their own time campaigning.
The party was standing candidates in every general electorate this year.
He was confident the money was so far well spent, with the party gaining momentum with voters as the campaign moves into the last four weeks.
In an interview yesterday, Mr Craig said the polls had the Conservatives ahead of where the party was polling before the 2011 election.
''Our internal polling is showing us at 4.5%. We caught New Zealand First for the first time last week.
"I am comfortable with our polling - it is bang on for getting us over 5%.''
Mr Craig said he was not naive and he spent Sunday campaigning in Napier on behalf of candidate Garth McVicar, formerly of the Sensible Sentencing Trust.
Mr McVicar had a ''good chance'' of winning the seat being vacated by National MP Chris Tremain. Former Labour MP Stuart Nash is also standing in the seat.
National did not do an electorate deal with the Conservatives, as it did with Act's Epsom candidate David Seymour and United Future leader Peter Dunne.
When Mr Craig was in Dunedin about a month ago, he told the ODT the Conservatives had 6000 members and supporters.
Yesterday, the party had 7500.
The party needs between 110,000 and 120,000 votes to get it across the 5% threshold and into Parliament if it does not win a seat.
South Island support was growing quickly following the mailing out of Conservative Party brochures, he said.
''We have so many forms coming back we can't process them all. We have boxes of them.''
One of the issues causing him angst this week was the start of National and Labour spending their $1 million of allocated taxpayer funding on television and radio advertising spots.
The Conservatives had been allocated a small amount of time but were unable to buy any more time on either television or radio, a situation he found unfair.
A better way would be to have a spending cap on how much individual parties could spend on advertising.
Mr Craig had been in discussions with the Electoral Commission on that and other areas of concern.
''The challenge for us in the next four weeks is working to get some cut-through. Let's just say we are working on this.''
Mr Craig believed his straight-shooting style of ''telling it like it is'' was striking a chord with South Island voters who wanted one law for all, wanted to be able to discipline their children and were not comfortable with land sales to foreigners.
Mr Craig campaigned in Balclutha and Gore yesterday and will be in Queenstown today and tomorrow.
